'What's Orphans?' asks Tom Waits, rhetorically, of his new three-disc, 54-song epic, in the accompanying 95-page booklet of lyrics and photographs. Answer: 'I don't know. Orphans is a dead-end kid driving a coffin with big tires across the Ohio River wearing welding goggles and a wife beater with a lit firecracker in his ear' - which probably sums it up as well as anyone else's attempt at classification might.

It is also an outstanding musical creation - 30 tracks are previously unrecorded - that nods to almost every known genre of American music, and some that have yet to be named, though to say so is pretty much a platitude at this stage in Waits's history. The late flourishing that began with the million-selling, Grammy-winning Mule Variations in 1999 has continued with rapturous acclaim for subsequent albums, including the most recent, 2004's Real Gone, where, with typical disregard for taste or fashion, he experimented with the supremely naff art of human beatboxing. Only a musician with Waits's vision and cachet could take a form that was previously the preserve of white teenagers aspiring to be ghetto and transform it into something feral and disturbing.

There is more beatboxing to be had here, notably on his cover of Daniel Johnston's 'King Kong', but Orphans has been helpfully arranged by genre, so that fans wanting to avoid too much of the avant-garde, the experimental, the monologues or shaggy dog stories can put to one side the third disc, 'Bastards', on which all such uncategorisable elements have been gathered and concentrate on the first two.

'Brawlers' is vintage roadhouse Waits: hard-edged, piano-and-guitar-driven rock and blues punctuated by wailing harmonicas, growling out stories of American misfits, cons and barflies with names like Blackjack Ruby and Scarface Ron, before giving way to swaying, whisky-rich laments of hobo life such as 'Lost at the Bottom of the World'. And then suddenly, in the midst of this classic Waitsiana, comes the most powerful and startling song of the entire collection, 'The Road to Peace'. The lyrics might have been lifted straight from newspaper reports (it begins, 'Young Abdel Madi Shabneh was only 18 years old' and goes on to namecheck Palestine's President Mahmoud Abbas, Ariel Sharon, Henry Kissinger and George Bush); the simple, repetitive drum and guitar backing recalls the rhythms of traditional Jewish tunes, and the result is one of those rare songs that roots you to the spot, makes your scalp prickle and produces an unearthly shiver in a warm room, which may well be the mark of great art. Waits once described the efficacy of political songs as 'like throwing peanuts at a gorilla', but this one is like hurling a rock into its face.

The second disc, 'Bawlers', is a casserole of country ballads, waltzes, spirituals and bar-room classics to rip your heart right out, including 'Goodnight, Irene' and a dirty, gritty version of 'The Long Way Home', reclaimed from Norah Jones's pleasant, sugary cover (which made it sound as if she were apologising for her train being slightly delayed). But the real fun is on the third disc, 'Bastards', which mixes up poems by Bukowski and Kerouac, a nature documentary detailing the homicidal tendencies of insects (analogy implied), a monologue, 'The Pontiac', in which an all-American father reminisces to his son about all the cars he ever owned, and finishes up with a truly bad joke that can't help but make you groan and smile just because of the relish with which he tells it.

Orphans is once again co-produced with Kathleen Brennan, his wife and collaborator. Two of his children, Casey and Sullivan, also contribute, respectively, drums and guitar, but the only instrument that matters here is, as ever, that extraordinary voice.